Fluid treatment devices and systems are known. For example, U.S. Pat. Nos. 4,482,809, 4,872,980 and 5,006,244, and U.S. patent application Ser. No. 08/026,572, now U.S. Pat. No. 5,418,370 (all assigned to the assignee of the present invention), the contents of each of which are hereby incorporated by reference, all describe gravity fed fluid treatment systems which employ ultraviolet (UV) radiation to inactivate microorganisms present in the fluid.
The devices and systems described in the '809, '980 and '244 patents generally include several UV lamps each of which are mounted within sleeves extending between two support arms of the frames. The frames are immersed into the fluid to be treated which is then irradiated as required. The amount of radiation to which the fluid is exposed is determined by the proximity of the fluid to the lamps. One or more UV sensors may be employed to monitor the UV output of the lamps and the fluid level is typically controlled, to some extent, downstream of the treatment device by means of level gates or the like. Since, at higher flow rates, accurate fluid level control is difficult to achieve in gravity fed systems, fluctuations in fluid level are inevitable. Such fluctuations can lead to non-uniform irradiation in the treated fluid.
However, disadvantages exist with the above-described systems. Depending on the quality of the fluid which is being treated, the sleeves surrounding the UV lamps periodically become fouled with foreign materials, inhibiting their ability to transmit UV radiation to the fluid. When fouled, at intervals which may be determined from historical operating data or by the measurements from the UV sensors, the sleeves must be manually cleaned to remove the fouling materials. Regardless of whether the UV lamp frames are employed in an open, channel-like system or a closed system, cleaning of the sleeves is impractical.
In open, channel-like systems, the modules comprising the sleeves are usually removed from the channel and immersed in a separate tank containing a suitable cleaning fluid. In closed systems, the device must be shut down and the sleeves are thereafter cleaned by charging with a suitable cleaning fluid or by removal of the lamps in the manner described for the open, channel-like system. In either type of systems the operator must accept significant downtime of the system and/or invest significant additional capital to have in place sufficient redundant systems with appropriate control systems to divert the flow of fluid from the systems being cleaned.
The system described in the '572 application is a significant advance in the art in that it obviates a number of disadvantages deriving from the devices and systems disclosed in the '809, '980 and '244 patents. Unfortunately, the system described in the '572 application is ideally suited for use in an open, channel-like system and is not readily adaptable to be used in a completely closed system where the flow of fluid is fed under pressure in a pipe.
It would be desirable to have a fluid treatment device which could be readily adapted to be treat a flow of fluid fed under pressure in a pipe or like enclosure. It would be further desirable if such a device was relatively easy to clean or keep clean during use.